Fix ogp_custom_meta_tags type warning

Author: AA-Turner

Doc/conf.py

@@ -567,13 +567,13 @@
     'image': '_static/og-image.png',
     'line_color': '#3776ab',
 }
-ogp_custom_meta_tags = [
+ogp_custom_meta_tags = (
     '<meta name="theme-color" content="#3776ab">',
-]
+)
 if 'create-social-cards' not in tags:  # noqa: F821
     # Define a static preview image when not creating social cards
     ogp_image = '_static/og-image.png'
-    ogp_custom_meta_tags += [
+    ogp_custom_meta_tags += (
         '<meta property="og:image:width" content="200">',
         '<meta property="og:image:height" content="200">',
-    ]
+    )